MAX 7219 broken?

Other Hardware Displays
1

Hi guys,

I recently bought a cheap 7-segment MAX 7219 tube (similar to this). I wrote a simple code to test its functionality, however it doesn´t do what it should (count to 999) but show some random numbers and stops showing anything after a few seconds.

I am using ths code:

#include <LedControl.h>

LedControl lc = LedControl(8, 10, 9, 1);
unsigned long delaytime=100;

void setup() {
  lc.shutdown(0, false);
  lc.setIntensity(0,8);
  lc.clearDisplay(0);
  Serial.begin(9600);
  
}
int digit(int a,int b){
  lc.setDigit(0,a,b,false);
}

int digit_dp(int a,int b){
  lc.setDigit(0,a,b,true);
}

void chrono() {
  lc.clearDisplay(0);
  int a=0;
  int b=0;
  int c=0;
  

  for (int timer=0;timer<999;timer++){
    a = timer % 10;
    int timer1 = timer/10;
    b = timer1 % 10;
    int timer2=timer1/10;
    c= timer2;

    digit(0,c);
    Serial.println(c);
    delay(delaytime);
    digit(1,b);
    Serial.println(b);
    delay(delaytime);
    digit(2,a);
    Serial.println(a);
    delay(delaytime);
    digit(3,0);

    delay(500);
  }
}


  


void loop() {
  chrono();
}

(I inserted a Serial print for easier debugging).

I dont have much experience with Arduino and especially the MAX 7219 chip, so my question is: Is there anything wrong with my code? Or could the MAX 7219 7-segment tube simply be broken?

Thanks
David

2

777-Pilot:
so my question is: Is there anything wrong with my code? Or could the MAX 7219 7-segment tube simply be broken?

Your code is very difficult to read since you seem to like to use variables with anonymous names that don't reflect their role.

I know what your code says about how your device is connected but is it connected the way the code says?

3

Hi, thanks for your answer.

Yes, the MAX 7219 is properly wired, since it does seem to work when only controlling one single digit at a time. I am pretty sure now that the chip is broken, I will simply test it with a new one.

4

777-Pilot:
I am pretty sure now that the chip is broken,

I have just used your code in a UNO connected to a 7219 controlled device the same as your referenced in your OP and it exhibits the same flaw you describe. By using my own test sketch I know my UNO and 7219 display are working so your software is faulty.

Edit : After some fault finding I'm not convinced the LedControl library is working correctly.

5

On my UNO the randomness disappears if I user pins 7, 6 and 5 instead of 10, 9 and 8 !